At-speed scan tests: A reality at LSI

Abstract

For 65 nm technologies and beyond, at-speed testing with high test coverage is a requirement for meeting low DPPM. Functional testing is not an option when it comes to merchant ASIC market. Functional vectors are time consuming to develop, need customer inputs, lack adequate coverage and time consuming to debug and deploy. Structural testing is our only option. Delay fault testing became a necessity for LSI, starting at the 0.18 mu node. Broadside transition delay fault testing run at tester clock rates was introduced for all products. Even though the observed overkill of TDF fails was close to 50% (validated with system level tests), the impact on reducing outgoing product quality was significant whilst at the same time the resultant yield impact was < 0.5%.